Recording to MKV - last GOP length vs actual stream duration

[displayholo]

In the last GOP of an OBS recording to MKV format it appears that a frame is missing, example below with defaults for H264 compression UHD at 60 framerate with a GOP length of 601.

Decoded frames for 3745,3746,????,3738

frame 3747 is omitted as it would have been encoded next if the GOP had not been closed early.

So my question is should the frame 3748 have been included if 3747 is omitted? Is it necessary or could it
cause a player to calculate a video stream duration of 3749 frames rather than the 3747 frames actually decodable, have I overlooked a method to synthesize frame 3747 when decoding, say by using concurrent P frames.

start of gop
read 0 frame 3600 (60000 PTS). I
....
read 145 frame 3746 (62433 PTS) P
read 146 frame 3745 (62417 PTS) B
read 147 frame 3748 (62467 PTS) P
end of gop
eof

Thank-You.